Что это за функция и как ее написать на с++?

#include <iostream>
#include <vector>
#include <algorithm>
using namespace std;
pair<long long, bool> min(const vector<long>& a, const vector<long>& b) {
pair<long long, bool> result{ 0, true };
if (a.size() != b.size()) {
result.second = false;
} else {
vector<long> diff;
for (size_t i = 0; i < a.size(); ++i) {
diff.push_back(static_cast<long long>(a[i]) - b[i]);
}
result.first = *min_element(diff.begin(), diff.end());
}
return result;
}
int main() {
const vector<long> a{ 2, 3, 4, 5, 7, 1, 5, 9, 8, 6 };
const vector<long> b{ 3, 9, 2, 4, 6, 7, 1, 5, 9, 4 };
const vector<long> c{ 1, 2, 1, 2, 1, 1, 2, 1 };
const auto good = min(a, b);
const auto bad = min(a, c);
if (good.second) cout << R"(Min for 'a' and 'b': )" << good.first;
else cout << R"(The sizes 'a' and 'b' do not match!)";
cout.put('\n');
if (bad.second) cout << R"(Min for 'a' and 'c': )" << bad.first;
else cout << R"(The sizes 'a' and 'c' do not match!)";
cout.put('\n');
cin.get();
}